Human locomotor activities such as walking, jogging and running, involves the largest muscles and bones in the body, and must be supported by the cardiovascular, respiratory, metabolic and nervous systems. This activity normally determines the capacity or condition, not only of the leg and backbones and muscles, but also of the heart, lungs and influences the amount of fat in the body and bloodstream. Knowledge of human locomotor activity is essential to both research and clinical practice in such diverse areas as physical conditioning, weight control, prevention of osteoporosis, cardio respiratory conditions, and the maintenance of condition of individuals in space flight.
The acquisition of knowledge of human locomotor activity has been hampered by the lack of a practical means for the continuous measurement of the key locomotor parameters. These parameters include the vertical foot/ground forces (F.sub.Z) generated in each step of the individual, as well as the number and rate of the steps over a prolonged period of, for example, 24 hours, or longer; as well as the lack of a practical means for determining the posture of the subject (lying, sitting or standing) during such activity. Also, the lack of practical means for determining the simultaneous effect of the activity on certain body systems, for example, heart rate, has also hampered the acquisition of the aforesaid knowledge.
In order to monitor human locomotor activity, it is essential that the vertical foot/ground forces (F.sub.Z) of the subject be measured over prolonged periods of time. Isolated measurements of the foot/ground forces of the subject have been made in the prior art by means, for example, of a "force plate", which comprises a platform with force recording elements between it and the ground. More recently, special shoes have been instrumented to measure the vertical foot/ground forces over a number of steps. However, such instrumented shoes are complex, custom made, difficult to use, and they have a high failure rate. Even if the problems of measuring the foot/ground forces over prolonged periods of time were solved, there still would remain in the prior art the problem of the practical recording, reproduction and manipulation of data over the prolonged period representing tens of thousands of cycles per day.
The present invention provides a practical means for solving the foregoing problems. Basically, the system of the invention continuously records the vertical acceleration (Gz) of the subject's center of gravity over the prolonged period. This represents a simple procedure as compared with any effort to record directly the vertical foot/ground forces (F.sub.Z) over such prolonged periods. The system then relates the characteristic acceleration signals of the locomotor steps of the subject with the foot/ground forces (F.sub.Z) associated with the individual's acceleration signature.
Accordingly, the system of the invention is capable of providing vertical foot/ground force data over prolonged periods of activity of the subject. Such foot/ground force data, as noted above, are essential in analyzing the effects of human locomotor activity on the muscles and bones of the body. In addition, the system of the invention provides data relating to other parameters of interest, such as the posture (lying, sitting or standing) and heart rate of the subject, as well as real time. A feature of the system of the invention is the provision of rapid means for processing and manipulating the data.
The embodiment to be described is concerned with vertical foot/ground force data because in most cases horizontal foot/ground forces are insignificant and may be neglected. However, it will become apparent as the description proceeds that the same techniques may be used to measure horizontal foot/ground forces, if so desired.